1. Field of the Invention
The present invention relates to electrical control devices such as rotary switches and more particularly to printed circuit contacts for attachment to such control devices and for providing an electrical connection to a printed circuit board.
2. Description of the Prior Art
Rotary switches and other control devices such as potentiometers and pushbutton switches are frequently used with printed circuit boards. To facilitate such use these control devices frequently include a plurality of printed circuit contacts each having a tail or terminal received in an aperture in the printed circuit board. The printed circuit contacts are intended to provide electrical connection between a rotatable contact disc of the rotary switch and the circuits of the printed circuit board. To provide for electrical contact between the rotatable contact disc of the rotary switch and the printed circuit contacts, one end of the printed circuit contacts includes a spring clip making sliding contact with the periphery of the disc.
During the manufacture of a printed circuit board employing a rotary switch, for example, the tails of the printed circuit contacts of the rotary switch are forced through apertures in the printed circuit boards such that the ends of the tails extend through the lower side of the circuit board. Solder is then applied to the lower surface of the circuit board to provide an electrical connection between the ends of the printed circuit contacts and the circuits of the printed circuit board.
Since the tail of the printed circuit contact is forced through the circuit board, the tail must be strong enough to resist bending under a substantial force. However, the jaws comprising the spring clip at the opposite end of the printed circuit contact must be substantially flexible. Each of the spring clips is intended to selectively receive the switch contact disc therebetween and the contact disc slides between the jaws of the selected spring clips. It will be appreciated that the jaws of the spring clips must be sufficiently resilient that they are biased against the surfaces of the contact disc to ensure a good electrical connection. However, the jaws of the spring clips must also be sufficiently flexible that they exert only a small force against the surfaces of the disc to avoid undue wear of the contact disc. If the jaws exert excessive pressure on the contact disc, the rotary switch will wear rapidly and have an unduly short life.
The spring clips and tails of the printed circuit contacts are generally comprised of full hard brass. Using full hard brass it has been found that it is generally necessary that the jaws of the spring clips be formed from material which is between 0.005 to 0.008 inches in thickness in order to provide the required flexibility and resilience to the jaws that they will maintain electrical contact with the contact disc yet avoid undo wear of the contact disc. However, when automated equipment is used to join control devices of the type having conventional printed circuit contacts to a printed circuit board, the tails of such contacts are usually insufficiently strong to withstand bending forces applied to them, when its ends are forced into apertures in a printed circuit board, unless the tails are formed of material substantially thicker than the material comprising the jaws of the spring clip.
Accordingly, prior art attempts to increase the resistance of the tails to bending have included forming the printed circuit contact in such a manner that the tail is comprised of two folded adjacent thicknesses of material as illustrated by the prior art printed circuit contact shown in FIG. 4. However, tails of such printed circuit contacts are still not sufficiently strong to withstand bending forces when the ends of the tails are forced into apertures of a printed circuit board using automated equipment. To further increase the strength of the tails, other prior printed circuit contacts have been comprised of two sections mechanically joined together, one part comprising the tail and the other providing the spring clip portion. However, such composite printed circuit contacts are too expensive to be commercially practical. Such printed circuit contacts are illustrated on page 8 of an advertizing publication from Oak Industries Inc., Switch Division, Crystal Lake, Ill. entitled Oak Sales Bulletin, 2 5/16 Diameter Rotary Switch Type MF (1974).